Name: how virus mutations drive outbreaks
Uploaded: 2019-03-11T09:21:24.000Z
Duration: 36 s
Channel: JoVE

K12 Standards

Louisiana Student Standards for Science

High School

Life Sciences

from-molecules-to-organisms-structures-and-processes

From Molecules To Organisms: Structures And Processes

HS-LS1-8

Viral Mutations

- [Instructor] Durante la replicación,

los virus pueden evolucionar
genéticamente por mutaciones,

cambios permanentes en
el material genético.

Más errores espontáneos ocurren
cuando el ARN está presente,

porque la replicación requiere

la enzima transcriptasa
inversa, la cual no se corrige,

lo que lleva a mayor probabilidad
de una evolución rápida

mARN viral - Traducción

y resistencia a los fármacos.

ENSAMBLADO

Este es el caso del virus de
inmunodeficiencia humana o VIH,

que lo hace difícil de combatir.

Quan, Chuansong, Weifeng Shi, Yang Yang, Yongchun Yang, Xiaoqing Liu, Wen Xu, Hong Li, et al. "Nuevas amenazas del virus de la influenza H7N9: propagación y evolución de variantes de alta y baja patogenicidad con alta diversidad genómica en la ola cinco". Revista de Virología 92, no. 11 (1 de junio de 2018): e00301-18. [<a href="https://doi.org/10.1128/JVI.00301-18" target="__blank">Fuente</a>]

mutaciones virales

Una mutación es un cambio en la secuencia de bases del ADN o ARN en un genoma. Algunas mutaciones ocurren durante la replicación del genoma debido a errores cometidos por las enzimas polimerasas que replican el ADN o el ARN. A diferencia del ADN polimerasa, el ARN polimerasa es propenso a errores porque no es capaz de "corregir" su trabajo. Por lo tanto, los virus con genomas basados en ARN, como el VIH, acumulan mutaciones más rápidamente que los virus con genomas basados en ADN. Debido a que la mutación y la recombinación proporcionan la materia prima para la evolución adaptativa, los virus basados en ARN pueden desarrollar rápidamente resistencia a los medicamentos antivirales. <h4>Comparar mutaciones nos permite reconstruir la evolución</h4> Un objetivo importante de la biología moderna es revelar la historia evolutiva comparando secuencias del genoma. Una aplicación práctica importante de estos análisis es el estudio de la evolución de los virus que causan enfermedades. La secuenciación del genoma se ha vuelto tan rápida y económica que ahora es posible investigar los orígenes y la evolución continua de los virus durante un brote de enfermedad. Por ejemplo, en 2013, surgió en China una nueva cepa de influenza aviar llamada H7N9 que causó enfermedades respiratorias graves en humanos. Al comparar las mutaciones en virus aislados de humanos y varias especies de aves, los investigadores pudieron demostrar que el antepasado de esta cepa de gripe probablemente se originó en poblaciones de patos domésticos chinos antes de que se transmitiera a los pollos. Posteriormente, la cepa ancestral se recombinó con otros virus de aves para generar la cepa H7N9 que infectó a los humanos. Estos análisis identificaron los mercados de aves de corral vivas como la fuente probable de infecciones humanas. Además, mientras investigaban la evolución de la cepa H7N9, los investigadores encontraron una cepa adicional de gripe aviar que probablemente puede infectar a los humanos. Este trabajo demuestra cómo los análisis evolutivos de mutaciones pueden proporcionar información crítica a los epidemiólogos durante una epidemia.

Mutaciones virales

Una mutación es un cambio en la secuencia de bases de ADN o ARN en un genoma. Algunas mutaciones ocurren durante la replicación del genoma debido a errores cometidos por el ...

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KEY TERMS AND CONCEPTS

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how virus mutations drive outbreaks

Virus mutations can change how quickly a virus evolves and spreads. A mutation is a change in the sequence of bases in DNA or RNA. Some mutations happen when the genome is copied. They are caused by errors made by polymerase enzymes, which replicate DNA or RNA.

RNA viruses often change faster than DNA viruses because RNA polymerase does not proofread its work. That means RNA-based genomes, such as HIV, can gather mutations more quickly. Mutation and recombination give viruses the raw material for adaptive evolution. As a result, RNA-based viruses can sometimes evolve resistance to antiviral drugs.

Scientists also use mutations to trace how viruses evolve over time. By comparing genome sequences, researchers can reconstruct evolutionary history. This is especially useful during disease outbreaks because genome sequencing is now fast and inexpensive. It helps scientists study where a virus came from and how it is changing.

The 2013 H7N9 avian influenza outbreak in China is one example. By comparing viruses from humans and several bird species, researchers found that the ancestor likely came from domestic ducks in China before spreading to chickens. That ancestral virus later recombined with other bird viruses to form the H7N9 strain that infected humans. The analysis also pointed to live poultry markets as the likely source of human infections and revealed another avian flu strain that may also infect humans.

How Virus Mutations Drive Outbreaks

what are viruses?

How Viruses Infect Cells and Multiply

Viruses infect cells and make new copies by using a host cell’s own machinery. A virus is a tiny infectious particle with an RNA or DNA genome inside a protective protein coat. It cannot reproduce on its own, so it must enter a cell to make more viruses. After infection, the virus sheds its protein coat and uses the host cell to transcribe and translate its genetic material. The cell then assembles many new viral particles. In many cases, these new viruses rupture the host cell and kill it.

viral structure

How Virus Shapes Help Infection

Viruses have specific structures that help them infect host cells and trigger immune responses. Each virus has a core that contains either a DNA-based or RNA-based genome. That core is surrounded by a protective protein coat called the capsid. The capsid is made of smaller subunits called capsomeres. The capsid and the genome-containing core together are called the nucleocapsid. Viruses are often grouped by capsid design. Most viruses have either icosahedral or helical capsids, but some have...

lytic cycle of bacteriophages

How Phages Infect and Burst Bacteria

Bacteriophages, or phages, are viruses that infect bacteria. They have a distinctive head-tail shape. In the lytic cycle, a phage first attaches to the outside of a bacterial cell. Tail proteins bind to specific receptor proteins on the bacterium’s surface. After attachment, the phage tail injects its DNA genome into the bacterial cytoplasm. The phage then uses the bacterium’s cellular machinery to make proteins needed for replication and dispersal. When phage replication is complete, some of...

lysogenic cycle of bacteriophages

Prophage Integration in Bacteria

The lysogenic cycle shows how bacteriophages can infect bacteria without killing the host right away. In this cycle, the phage genome joins the bacterial genome. The integrated phage DNA is called a prophage, and the bacterium copies it each time it replicates. Some prophages can switch back into the lytic cycle. This change can happen after DNA damage or even without an obvious outside trigger. When the prophage is induced, the phage begins making new virus particles again. Prophages can...

retrovirus life cycles

How Retroviruses Replicate in Host Cells

Retroviruses replicate by copying their RNA genome into DNA inside a host cell. After entry, the viral enzyme reverse transcriptase makes a double-stranded DNA copy from the single-stranded RNA genome. The viral DNA is then carried into the nucleus and inserted into the host genome by integrase. Once integrated, the retroviral DNA is transcribed whenever the host genome is transcribed. This produces new viral RNA that can be copied and used again. The new RNA moves into the cytoplasm, where it...

viral recombination

How Viruses Swap Genes and Spread

Viral gene swapping can happen when more than one virus infects the same cell. After the viruses break open and expose their genomes for replication, matching regions can pair up and exchange sequences. This process is called recombination. Viruses with segmented genomes can also swap whole segments, which is called reassortment. These changes can help create new diseases. Some diseases can infect more than one species. Pigs can be infected by some human and bird viruses, along with the...

viral mutations

Virus mutations can change how quickly a virus evolves and spreads. A mutation is a change in the sequence of bases in DNA or RNA. Some mutations happen when the genome is copied. They are caused by errors made by polymerase enzymes, which replicate DNA or RNA. RNA viruses often change faster than DNA viruses because RNA polymerase does not proofread its work. That means RNA-based genomes, such as HIV, can gather mutations more quickly. Mutation and recombination give viruses the raw material...

key terms and concepts

Learn how RNA and DNA virus mutations differ, why RNA viruses evolve fast, and how genome sequencing helps track outbreaks like H7N9 influenza.

How Virus Mutations Drive Outbreaks | JoVE K12

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Heredity: Inheritance and Variation of Traits

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HS-LS1-2

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HS-LS1-4

How Virus Mutations Drive Outbreaks

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